Silencer



1", 1943. j. G. BLANCHD July SILENCER Filed Ooi. 9, 1940 5 Sheets-Sheet 1 Q D @u A from/EY July 13, 1943. J. G. BLANCHARD 2,323,891

SILENCER Filed Oct. 9, 1940 3 Sheets-Sheet 2 DL-PPV??? @d E@ LL.

Patented July 13, 1943 SILENoEn Joseph George Blanchard, London, England, assignor of one-half to Cecil Gordon Vokes, London, England Application October 9, 1,940, Serial No. 360,488 'j In Great Britain October 13, 1939 4 Claims.

This invention relates to silencers for us` in silencing noise caused by pulsating gaseous currents. It is primarily intended for silencing the exhaust of internal combustion engines of fastmoving vehicles such as aircraft or -fast cars and speed boats.

Various considerations are of importance in such silencers. Lightness, easy cooling while serving as a flame trap, effective emission of the gases, and small resistance to air ilow past the external surfaces are examples of such, considerations.

Silencers according to the invention have outer surfaces which are ridged or corrugated, with the ridges running in substantially the direction of air iiow past the surface; and a number of backwardly directed apertures through which the gases emerge are formed in the ridges, preferably bff bending down into the ridge a forwardly facing lip or tongue or the forwardly facing edge of a straight or concave or backwardly inclined slit. The outer surface of the ridge can thus show no protuberances, while the bent down edge gives a backward and outward direction to the gases and enables the air iiow past the apertures to help their emergence. Preferably the gases have already been allowed to expand before they enter the channels behind, the ridges and are distributed along the channels by apertures leading into them. A simple construction for this purpose is to 'use rather steeply corrugated sheet metal backed by a perforated sheet. The corrugations will preferably not be of considerable height but many in number Where air resistance is of primary importance.

It will be noted that the ridging gives a large surface and effective cooling, so that a relatively light sheet heat resisting material will stand up to the heat of the expanded gases, and that the cooling and scavenging action should help the flame trap function and produce an exhaust system relatively safe from the point of view of re.

One typical application would be the use ofthe proposed corrugated and, backing sheets as the outer cover member of a. conventional silencer, or as panels forming the sides of such a cover member.

Another typical application would be to -the tubular type of exhaust, the tube being suitably perforated over its whole surface or over a selected part and the corrugated material covering the perforations.

Another would be its use for the emission of direction of the corrugations naturally taking into account any rotary component of the air flow, so that the air moves substantially longitudinally of them.

Numerous other applications of the invention to different types of silencer will suggest themselves.

It is generally preferred in each case to form the apertures by pushing in the crown of the ridge of each corrugation behind a series of cuts, so as to produce a series of backwardly sloping Vs in elevation.

Other parts of the invention are embodied in and objects will be apparent from the examples of its application in practice which will now be described with reference to the accompanying drawings, in which:

' Fig. l is an elevation, partly in section, of a simple form for receiving the exhaust of four cylinders or groups of cylinders and combining the functions of silencer, cooler and flame trap,

Fig. 2 is an end view of the same,

Fig. 3 is an elevation, partly cut away, of a form suitable for attachment to a, forwardly iacing exhaust from a cylinder of a radial engine,

' Fig. 4 is an end view of the same,

Fig. 5 is a plan, partly in section, of a form which might serve as a substitute for a fish-tail end to an exhaust pipe, and

Fig. 6 is an end view of the same.,

In each case the ridges I are disposed in substantially the direction of air ow past the silencer, which may, if considered desirable, take into account any rotary component of the air flow, so that the air moves substantially longitudinally of them. The backwardly directed apertures 2 are shown as formed by bending down the forwardly facing edge of a straight slit. Apertures 3 lead the exhaust into the ridges l.

As shown in Figs. l and 2 the four pipes 4 are each arranged to be connected to a cylinder or group of cylinders of an engine and lead the exhausts into the expansion chamber 5 from which they escape through the apertures 3 into the ridges I and are thence drawn out through apertures 2. A preliminary cooling is arranged for in this case by an air pipe S which receives cold air, as the aircraft (the cowling of which is represented at l) or vehicle moves forward, at the end 6a and discharges hot air ,(of which use may be made, for example in warming the air passing to the Carburettor or cylinder intakes or for warming cabins or instruments) at the end 6b.

As shown at Figs. 3 and 4 the pipe 4 is arranged to he connected to an individual cylinder exhaust of a radial engine and forms the first part of the tubular expansion chamber 5. This chamber is shown tapered ofi and finally closed by gradually doubling in the lower part of the wall towards the upper part until nally pressed into Contact as can be seen from Fig. 4. The ridged outer walls i are secured over the apertures Sand project into the air outside the engine Cowling whose position is indicated at l.

For Connection to an exhaust facing other than i. such air flow.

2. A construction as dened in claim l, whereforwardly it is clear that it is only necessary to face the pipe 4 in the appropriate direction.

Figs. 5 and 6 show a simple form winch is suit able for connection to the end of an exhaust pipe. The chamber 5 is closed and has its cross-sectional area reduced towards the back. of the vehicle or aircraft by a forwardly directed cone The whole of this form may conveniently be exposed to the air ow.

The arrows in each case indicate the direction of air now relatively to the device when the aircraft or other vehicle is moving forward: it will.

and the imperforate walls of the ridges insuringl an uninterrupted cooling of the ridge incident t0 in the apertures in the crowns of the ridges are backwardly directed relative to air flow.

3. A construction as defined in claim 1, wherein the area of the expansion chamber is reduced toward the rear relative to the direction of air ow.

4. A construction as donned in claim 1, wherein a pipe passes through the expansion chamber and is` directly open to the air fiow to form a cooling air passage in such chamber.

JOSEPH GEORGE BLANCHARD. 

